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5 functions of Skeletal system
- 1. Support
- 2. protection
- 3. leverage
- 4. blood cell production
- 5. mineral and lipid storage
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context: 5 functions of Skeletal system
support
structural support; attachment for connective tissue
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context: 5 functions of Skeletal system
protection
surround organs
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context: 5 functions of Skeletal system
leverage
function as levers to move loads
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context: 5 functions of Skeletal system
blood cell production
hematopoiesis in red bone marrow
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context: 5 functions of Skeletal system
mineral and lipid storage
- body's reserves fro calcium (99%) and phosphate (88%)
- storage of lipids in yellow bone marrow
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Gross anatomy of bones is classified by which of the following:
1. size
2. shape
3. strength
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6 shapes of bones
- 1. long
- 2. short
- 3. flat
- 4. sutural
- 5. irregular
- 6. sesamoid
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context: 6 shapes of bones : location
long
- 1) upper arm
- 2) forearm
- 3) legs
- 4) hands
- 5) feet
- 6) fingers
- 7) toes
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context: 6 shapes of bones : location
short
- 1) carpals (wrist)
- 2) tarsal (ankle)
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context: 6 shapes of bones : location
flat
- 1) facial
- 2) skull
- 3) sternum
- 4) jaw
- 5) ribs
- 6) scapula
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context: 6 shapes of bones : location
sutural
between sutures in skull
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context: 6 shapes of bones : location
irregular
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context: 6 shapes of bones : location
sesamoid
patella
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context: bone anatomy
2 bone types
- 1. compact bone
- 2. spongy bone
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context: 2 bone types
compact bone
- hard, outer portion
- 80% bone mass
- 20% surface area
- parallel stress; not perpendicular
- Appendicular skeleton
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context: Structure of Compact bone
3 types of lamellae (layers of matrix)
- 1. concentric - central canals
- 2. interstitial - no central canals
- 3. circumferential - no central canals
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context: 2 bone types
spongy bone
- lighter, inner portion and bone ends
- 20% bone mass
- 80% surface area
- multidirectional stress
- Axial skeleton
- ----
- no osteons but rather trabeculae (no capillaries, but struts for strength).
- in between is bathe in bone marrow (red and yellow).
- red: all at birth
- yellow: 50% in adults
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2 types of bone coverings
- 1. periosteum
- 2. endosteum
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context: 2 types of bone coverings
periosteum
- outside of compact bone
- EXCEPT in joints
- peri/perimeter!
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4 functions of periosteum
- 1) isolates bone from surrounding tissue
- 2) provides route for vessels and nerves
- 3) anchors bone to tendons and ligaments
- 4) active in growth, repair, remodeling
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context: 2 types of bone coverings
endosteum
medullary cavity and central canal
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2 functions of endosteum
- 1) lines marrow cavity and central canal
- 2) active in growth, repair, remodeling
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4 types of bone cells
- (building up bone)
- 1. osteoprogenitor
- 2. osteoblasts
- 3. osteocytes
- ----------
- (destroying down bone)
- 4. osteclasts
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context: 4 types of bone cells
osteoprogenitor
- bone stem cell
- -can convert to osteoblasts
- found in: endosteum or periosteum
- -----
- origin: mesenchymal cells
- location: cellular layer of periosteum, endosteum, and linings of canals
- function: stem cells of bone (differentiate into osteoblasts)
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context: 4 types of bone cells
osteoblasts
- bone builders
- form new bone
- immature bone cell that secrete organic components of matrix (to become bony matrix)
- found in: perimeter
- -------
- origin: osteoprogenitor cells
- location: periosteum and endosteum
- function: osteogenesis: production of bone matrix (fibers + ground substance)
- Process: initially, matrix is primarily organic (collagen) called osteoid
- then calcium salts are deposited (calcium phosphates)
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context: 4 types of bone cells
osteocytes
- bone maintenance
- -osteoblasts turn into after encased in bone
- mature bone cell that maintains the bone matrix
- found in: in lacunae (stuck) only in matrix because they get stuck (they were osteoblasts).
- -----
- origin: develop from osteoblasts (mature bone cells surrounded by matrix)
- location: lacunae in matrix (osteocytes connects via canaliculi, passageways in the matrix to other lacunae and blood vessels to outer osteoblasts and through gap junctions can get transport of nutrients and waste.)
- functions:
- 1) monitor and maintain mineral and protein content of matrix (continual turnover of bone)
- 2) repair damaged bone (leave lacunae and convert back to osteoblasts ---WHAAA??? that's some crazy nonsense, but it's true!)
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context: 4 types of bone cells
osteoclasts
- bone demolition
- multinucleated cell that secretes acids and enzymes to dissolve bone matrix
- found in: medullary cavity
- ------
- origin: related to myloid stem cells/monoblasts (same as for monocytes/macrophages) - notably multinucleated!
- location: endosteum, periosteum
- function: osteolysis - removal and recycling of minerals and bone matrix - secrete acids and proteases to dissolve matrix
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- See if you can tell if you covered up the words and know what each are! :D
- oooo exercising your brain!
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3 parts of bone in gross anatomy
- 1. epiphysis - ends
- 2. diaphysis - shaft
- 3. metaphysis -between/middle of diaphysis-epiphysis
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context: bone matrix
lamellae
layers of matrix
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2 components of bone matrix
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context: 2 components of bone matrix
organic components
- 33% of bone weight
- collagen fibers (very small amount of cells)
- tough, but flexible
- tolerates twisting and bending
- scaffolding for crystal formation
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context: 2 components of bone matrix
inorganic components
- 67% of bone weight
- Calcium phosphate
- + calcium hydroxide = hydroxyapatite
- during formation of these crystals: CaCO3, Na+, Mg2+, F- are incorporated
- This makes bone hard and inflexible; brittle and resists compression
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NOTE: calcium dominates in inorganic component of bone matrix
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Bone development overview
- bony skeleton starts to form 6 weeks after fertilization
- cartilage before bone
- portions of bone do not stop growing until ~25 years
- remodeled for lifetime!!
- you get ossification from cartilage or fibrous connective tissue or mesenchyme
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context: bone formation and growth
2 types of ossification
- 1. endochondral ossification
- 2. intramembranous ossification
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context: 2 types of ossification
endochondral ossification
- most bones (long bones)
- bones replacing existing cartilage
- -----
- Long bone formation
- Hyaline cartilage converted to bone
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context: 2 types of ossification
intramembranous ossification
- flat bones
- develops from fibrous connective tissue or mesenchyme (not from cartilage precursor)
- -------
- formed in the deep dermis
- the mesenchymal cells secrete matrix
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context: bone formation and growth
calcification
- deposition of calcium salts
- -occurs during ossification
- -can occur in other tissues (ex: heart with ionic imbalances from kidneys)
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2 types of supporting connective tissues
- 1) cartilage - solid, rubbery matrix (hyaline, elastic, fibrocartilage) Fig. 4-15
- 2) bone - solid, crystalline matrix Fig. 4-16
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context: 2 types of supporting connective tissues
cartilage
- 1. matrix:
- -ground substance: Chondroitin Sulfate (firm gel)
- -fibers: collagen, elastic, reticular
- 2. cells:
- -Chondrocytes (in lacunae)
- 3. Avascular
- -Chondrocytes produce antiangiogenic factor
- 4. reparability
- -limited
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context: 2 types of supporting connective tissues
bone
- 1. matrix:
- -ground substance (2/3): calcium phosphate and calcium carbonate
- -fibers (1/3): collagen
- 2. cells:
- -osteocytes (in lacunae)
- 3. vascular:
- -higher energy demands than cartilage
- 4. reparability:
- -extensive
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context: supporting connective tissue
3 types of cartilage
- 1. elastic
- 2. hyaline
- 3. fibrous
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context: 3 types of cartilage
elastic cartilage
- matrix: elastic fibers
- attribute: resilient and flexible
- location: external ear, epiglottis, larynx, auditory tube
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context: 3 types of cartilage
hyaline cartilage
- MOST COMMON
- matrix: densely packed collagen fibers
- attribute: tough, somewhat flexible
- location: ribs to sternum, nasal septum, joints, airways
- (intermediate between other 2 types -semi flexible and tough but not inflexible)
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context: 3 types of cartilage
fibrous cartilage
- matrix: dense, interwoven collagen; decreased ground substance
- attribute: very tough and durable, resists compression, absorbs shock
- location: between vertebrae, pubic symphysis, knees
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2 ways for cartilage to grow
- 1. appositional
- 2. interstitual
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context: 2 ways for cartilage to grow
appositional
- 1 .cartilage added just beneath the surface of the perichondrium
- 2. stem cells in the inner layer of perichondrium divide and differentiate into immature chondroblasts (secrete new matrix)
- 3. chondroblasts mature into chondrocytes
- 4. mostly occurs in utero
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context: 2 ways for cartilage to grow
interstitial
- 1. chondrocytes in matrix divide
- 2. new matrix secreted
- 3. in utero development through adolescence
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Bone remodeling overview
- Occurs for lifetime
- - 20% is turned over each year = 5 years to all turnover
- -not all parts of bone is affected equally: more in femurs (spongy bone replaced 2-3 times a year)
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context: Bone remodeling
5 reasons for varying remodeling
- 1. age of individual
- 2. physical activity and exercise
- 3. circulating hormone levels
- 4. rate of calcium and phosphate absorption/excretion
- 5. genetic mutations or environmental factors
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context: 5 reasons for varying remodeling
age of individual
- childhood: deposition > resorption
- maturity: deposition = resorption
- aging: deposition < resorption
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context: 5 reasons for varying remodeling
physical activity and exercise
- stressed bones become thicker and stronger
- stronger attachment sites for tendons
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context: 5 reasons for varying remodeling
circulating hormone levels
- alter the rate of deposition and resorption
- endocrine disorders often affect the skeletal system
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context: 5 reasons for varying remodeling
rate of calcium and phosphate absorption/excretion
- for bone mass to remain constant, this must be balanced
- renal problems can impact skeletal system
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context: 5 reasons for varying remodeling
genetic mutations or environmental factors
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3 metabolic bone disorders
- 1. osteomalacia
- 2. osteopenia
- 3. osteoporosis
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context: 3 metabolic bone disorders
osteomalacia
- softening of the bones due to a lack of or inability to utilize vitamin D/cholecalciferol
- ex: rickets: osteomalacia in children
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context: 3 metabolic bone disorders
osteopenia
- mild reduction in bone density
- begins in 30s-40s
- osteoblasts slow down, osteoclasts do not
- women lose 8% per decade; men lose 3% per decade
- may progress to osteoporosis
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context: 3 metabolic bone disorders
osteoporosis
- severe reduction in bone density
- -effects function
- -------
- "porous bone"
- normal mineralization, but bone density decreased (generalized or localized)
- ~10 million Americans and 34 million more at risk
- $17 billion/ year for costs
- MOST COMMON metabolic bone disorder
- resorption > deposition
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The risk factors of osteoporosis can be broken down to 2 types
- 1) non-modifiable
- 2) modifiable
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context: 2 types of risk factors for osteoporosis
6 non-modifiable
- 1. gender (females)
- 2. race and genetics (asians/caucasians > hispanics > african americans
- 3. family history
- 4. advancing age
- 5. post-menopausal
- 6. small frame
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context: 2 types of risk factors for osteoporosis
4 modifiable (things you can and should do to fix)
- 1. inadequate diet
- 2. alcohol, smoking, caffeine
- 3. inadequate physical activity
- 4. medications (ex: gluticorticoids, Warfarin, H+ pump inhibitors)
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3 basic types of osteoporosis
- 1. type 1 - post-menopausal
- 2. type 2 - age-related
- 3. type 3 - secondary
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context: 3 basic types of osteoporosis
type 1
- cause: low hormone levels
- incidence: 50-70 yrs (women 3-6x)
- bone affected: spongy > compact
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context: 3 basic types of osteoporosis
type 2
- cause: age
- incidence: 70+ yrs (women 2x)
- bone affected: spongy = compact
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context: 3 basic types of osteoporosis
type 3
- cause: medications, disease states
- incidence: variable
- bone affected: variable
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treating osteoporosis
- vitamin D3
- Greater calcium/vitamin d in diet or environment
- exercise
- reduce or eliminate modifiable risk factors (alcohol, caffeine, smoking)
- hormone replacement therapy
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